An important part of the job as a front-end developer is to stay up to date and in contact with new tools, trends and workflows. That’s why you cannot miss this upcoming webinar to explore the latest trends in UI technologies!

>> so that means I don't need to add ActionListener to the new items??
The actionlistener listens to actions happening on *the combobox* no matter how many items are in it

>> if I want to remove the new item
To remove you can use
void removeItem(Object anObject)
or
void removeItemAt(int anIndex)

For the first you have to pass the object that is in it
For the first you only need to pass the index

>>How can I know whether the new item I wanna add is existing in a JComboBox so I won't add another one again??
Whenever you add an item to it or remove an item from it, you could also add/remove it from a Set.
Then before adding you could look if it exists in the set. If so, you shouldn't add it anymore.
(The Set is for not having to interrogate each item of the Combobox to check if the item you want to insert is already in)

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